Test devices known as spinstands are used to test and evaluate magnetic disks and magnetic heads used in hard disk drives, as well as other structural and functional components of drives. The disks generally include a relatively rigid disk having two parallel planar principle surfaces, and bearing a magnetic medium on at least one of the principle surfaces. In the spinstand, a spindle is driven by a motor to rotate about a disk axis, as data is written to and read from the disk, and evaluated. At such rotation rates, it is important to maintain mechanical stability of the disk, minimizing vibration, so that desired test procedures can be applied, and accurate testing measurements can be obtained.
It also is important to be able to reconfigure a spinstand relatively quickly, for example, on a factory floor, so that various thickness magnetic media disks can be tested in succession on a given spinstand. For example, it may be necessary to analyze disks of a first thickness X, followed by disks of second thickness Y, followed by disks of a third thickness Z.
In accordance with prior art, a disk-under-test is placed on a chuck and clamped by a chuck cap to the spindle. The spindle is driven to rotate about a spin axis of the spinstand by the drive motor.
In conventional practice to maintain stability of a rotating disk on a spinstand, a plate having an at least “nominally” flat bearing surface is disposed opposite and preferably parallel to the planar underside of the disk, maintaining a small gap G, between the bearing surface and the planar underside of the disk. Hard drives use a gap between 0.005 inch and 0.010 inch. Smaller gaps are harder to achieve in mass production and the spindle motor draws a lot of power with such gaps. As “nominally” flat, the bearing surface may be smooth (for example, highly polished planar), or it may be textured, but is considered “nominally” flat, or just “flat” as used herein.
With such a configuration, an air bearing is established between the planar underside of the disk-under-test and the bearing surface, providing a high degree of mechanical stability, minimizing vibration of the disk, during the test process. In accordance with conventional practice, a spinstand is set up to accommodate a disk of a given thickness so that the underside of the disk is opposite the bearing surface, with the bearing surface being parallel to the underside and with a desired gap G between the bearing surface and the underside of the disk.
There are, however, at least two significant problems with such practice.
First, it is very difficult, and time-consuming and thus costly, to establish such a parallel configuration for a first disk-under-test having a first thickness and/or diameter. Generally, in the prior art, a support structure for a given disk is typically composed of multiple elements, including shims, for fine adjustments.
Second, when testing a succession of disks, after testing the first disk, the repetition of those alignment steps is required to establish a similar configuration for a second disk-under-test of a different thickness and/or diameter. Generally, in the prior art, in order to accommodate a succession of differing thickness and/or diameter disks, an entire assembly for supporting the plate having the bearing surface, must be reconfigured to accommodate the various thicknesses and/or diameter of the disks in the succession.
In view of the need to continually develop equipment and methodologies suitable for effecting cost-efficient design and testing of magnetic read/write heads and disks, it is increasingly important to provide a solution to the above noted difficulties.